1. Field of the Invention
The present invention relates to a hole filling blind rivet.
2 Description of the Prior Art
Blind rivets are widely used in fastening applications where one side of the workpiece is inaccessible. Typically the blind rivet includes a mandrel (also called a stem or spindle) and a surrounding rivet sleeve or body which together are inserted through a hole in the workpiece. The exposed end of the mandrel has shallow annular grooves engaged by a riveting tool equipped with a pulling head. As the mandrel is pulled, the inserted end of the mandrel mechanically expands the sleeve against the inaccessible side of the workpiece. Meanwhile a conical groove on the mandrel is translated toward a complimentary surface provided in the manufactured head of the sleeve. At the instant that these two interacting surfaces mate to provide sufficient opening, a collar is driven into the void. The mandrel is now incapable of either forward motion by continued pulling or recoil when it snaps at a predetermined breaknotch. Sleeve, mandrel and collar now become a secure unit imparting strength to the joint.
In the inventor's U.S. Pat. No. 3,880,042 there is disclosed a blind rivet in which sets of lugs are mutually radially and axially offset. As the mandrel is pulled, these sets of lugs expand the sleeve in a radially non-uniform pattern to form a bulb at the blind surface of the workpiece.
One embodiment of the rivet shown in that U.S. Pat. No. 3,880,042 was intended as a hole-filling bllind rivet. The objective was to provide a rivet which would eliminate any gap between the installed sleeve and the hole in the workpiece through which the rivet was inserted. In that embodiment, a portion of the mandrel between separated sets of lugs was geometrically configured with a maximum diameter slightly greater than the inner diameter of the sleeve. As the mandrel was pulled during rivet installation, the first set of lugs sheared and translated axially rearwardly along the mandrel. Subsequent to the shearing of the first set of lugs, the enlarged diameter mandrel portion urged radially expansion of the sleeve to accomplish hole filling. Thereafter, the second set of lugs completed bulb formation by radially expanding the sleeve in different sectors than those expanded by the first set of lugs.
An object of the present invention is to provide an improved type of hole filling blind rivet.
In the inventor's U.S. Pat. No. 3,915,055, there is a disclosed a blind rivet having a counterboard sleeve head of double-angle configuration. Using such a counterbored sleeve head permitted the blind rivet to be installed with a non-shifting pulling head such as that disclosed in the inventor's U.S. Pat. No. 3,850,021. During the initial phase of rivet installation, the locking collar pressed against the outer conical surface of the sleeve counterbore. This surface defined a relatively shallow locking collar entry resistance angle, so that most of the force of the pulling head was exerted in a direction axially of the mandrel, so as to obtain most efficient installation. During a subsequent phase of the installation, the inner conical surface of the sleeve counterbore was aligned with the locking groove in the mandrel. This facilitated guiding insertion of the locking collar into the groove.
Another object of the present invention is to provide an improved type of sleeve counterbore configuration for reception of the locking collar.